Weed Implicated in Potato Blight
Persistence By Erin Peabody December 12, 2006
Late blight, the devastating tuber disease that triggered the Irish
potato famine of the mid-1800s, has a new partner in crime.
Scientists with the Agricultural Research Service (ARS) in Orono, Maine, discovered that
Phytophthora infestansthe microorganism behind the spud-spoiling
diseaseis seeking refuge in potato fields, holed up in an alternate host
plant: hairy nightshade.
Best known for causing widespread hunger, illness and death in 1840s
Ireland, P. infestans continues to pose a formidable threat to global
potato and tomato production. According to the
International Potato Center in Lima,
Peru, the disease costs the world's growers more than $3 billion each year in
fungicides and other control measures.
Olanya, a plant pathologist at the ARS
England Plant, Soil and Water Research Laboratory in Orono, learned of the
possibility of an alternate host in 2004 from colleagues at the
University of Maine Cooperative
Extension in Presque Isle.
As extension agents in the northern part of the state discovered,
hairy nightshade plants were showing up speckled with suspicious dark and oily
spots. Olanya analyzed the microorganisms on the plants and verified, for the
first time, that hairy nightshade is an alternate host of P. infestans
To make matters worse, hairy nightshade is hardly a wallflower, in
terms of its presence in commercial potato fields in Maine. In a limited
survey, Olanya and University of Maine
collaborators found that 55 percent of fields assessed in the state contained
According to Olanya, the finding that hairy nightshade is an active
host of P. infestans is problematic in two ways. First, the plant is a
secondary source of the destructive disease. And, it's a weed.
As a result of this ARS research, growers are now learning the
importance of controlling hairy nightshade as part of their overall late blight
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.